This report provides information to increase understanding of the public health impact of Alzheimer's disease (AD). Topics addressed include incidence, prevalence, mortality rates, health expenditures and costs of care, and effect on caregivers and society. The report also explores issues that arise when people with AD and other dementias live alone. The characteristics, risks, and unmet needs of this population are described. An estimated 5.4 million Americans have AD, including approximately 200,000 age <65 years who comprise the younger-onset AD population. Over the coming decades, the aging of the baby boom generation is projected to result in an additional 10 million people with AD. Today, someone in America develops AD every 68 seconds. By 2050, there is expected to be one new case of AD every 33 seconds, or nearly a million new cases per year, and AD prevalence is projected to be 11 million to 16 million. Dramatic increases in the number of "oldest-old" (those age ≥85 years) across all racial and ethnic groups are expected to contribute to the increased prevalence of AD. AD is the sixth leading cause of death in the United States and the fifth leading cause of death in Americans age ≥65 years. Although the proportions of deaths due to other major causes of death have decreased in the last several years, the proportion due to AD has risen significantly. Between 2000 and 2008, the proportion of deaths due to heart disease, stroke, and prostate cancer decreased by 13%, 20%, and 8%, respectively, whereas the proportion due to AD increased by 66%. In 2011, more than 15 million family members and other unpaid caregivers provided an estimated 17.4 billion hours of care to people with AD and other dementias, a contribution valued at more than $210 billion. Medicare payments for services to beneficiaries age ≥65 years with AD and other dementias are three times as great as payments for beneficiaries without these conditions, and Medicaid payments are 19 times as great. In 2012, payments for health care, long-term care, and hospice services for people age ≥65 years with AD and other dementias are expected to be $200 billion (not including the contributions of unpaid caregivers). An estimated 800,000 people with AD (one in seven) live alone, and up to half of them do not have an identifiable caregiver. People with dementia who live alone are exposed to risks that exceed the risks encountered by people with dementia who live with others, including inadequate self-care, malnutrition, untreated medical conditions, falls, wandering from home unattended, and accidental deaths.